The world’s biggest nuclear power station stands directly above an active earthquake faultline, which provoked an atomic spill this week, seismologists revealed yesterday.

The disclosure that the Kashiwazaki plant was prone to further earthquake damage threw Japan’s nuclear industry into crisis as seismologists recommended that up to a third of the country’s 55 atomic power stations should be closed for inspection.

In addition to the seismic threat to the Kashiwazaki plant, scientists identified an active threat to one of Japan’s oldest nuclear power stations and demanded that it should be closed immediately.

The former head of the country’s top authority on earthquake prediction told The Times that the Shizuoka plant posed a serious safety risk and that atomic experts were calling for it to be shut down.

Professor Kiyoo Mogi, of Tokyo University, the former chairman of the Co-ordinating Committee of Earthquake Prediction Japan, said it was “hard at this stage to say how many nuclear power plants should be stopped”. He added: “But I can say Hamaoka power plant in Shizuoka should be stopped immediately.”

The precarious state of the Kashiwazaki plant was underscored by an earthquake on Monday that knocked over hundreds of drums of nuclear waste, many of which split open during the tremors. The town’s mayor ordered all activity at the power station to be suspended indefinitely. It was shut down temporarily during the quake.

The suspension, and the threat of widespread disruption to nuclear plants around the country, was likely to herald “a hot summer of blackouts” in parts of central Japan, according to energy analysts. The power shortages would affect factories and businesses across the region. Japan, which has almost no oil or gas reserves, generates 33 per cent of its electricity in nuclear power stations, but the Government hopes to increase this to 40 per cent by 2010.

The revelations of Kashiwazaki’s geological weakness dealt a massive blow to the credibility of the Tokyo High Court and to the National Institute of Advanced Industrial Science and Technology — the government- affiliated body whose survey showed the fault to be about 15km (nine miles) from the plant.

In 2005, fearing the effects of a large quake, a group of residents fought to have Kashiwazaki’s license to build a new reactor revoked. The Tokyo High Court rejected the plaintiffs’ claim that an active fault ran under the station, concluding that what the residents thought was an active fault “did not even amount to a fault and could not cause a quake”. Atomic experts said yesterday that the discovery may dramatically challenge the safety of the entire atomic energy supply in Japan and that as many as a third of the country’s 55 nuclear power stations might have to be suspended until they were made sufficiently quake-proof to be restarted.

The chaotic response by the Tokyo Electric Power Company (Tepco) to the earthquake and its after-effects prompted Mohamed ElBaradei, the Director-General of the International Atomic Energy Agency, to demand that Japan should conduct a full examination of the plant. “Japan needs to go into full investigation of the structure, of the systems, of the components of the reactor,” he said, offering to send a team of IAEA experts to assist.

Reflecting growing concerns that Tepco may be unaware of or has concealed the extent of the damage at Kashiwazaki, Dr ElBaradei added: “I would hope that Japan would be fully transparent in its investigation of the accident.” The catalogue of problems so far discovered by investigators at Kashiwazaki includes several leaks of radioactive materials, a fire, and the toppling of 438 drums of low-level radioactive waste. Hiroshi Aida, the Mayor of Kashiwazaki, said that his staff’s own investigation had found that the ground on which the plant was built had been distorted and suffered several cave-ins.

The Japanese Government fiercely attacked the sloppy response of Tepco.

Akira Fukushima, the deputy director-general for nuclear safety, said: ”We definitely think the report from Tepco was delayed, and this is very serious.”

Hunger for energy

— Japan imports 80 per cent of primary energy needs

— It began a nuclear power programme in 1954. Its first commercial reactor, a 160MWe model imported from Britain, came on line in 1966

— The “oil shocks” beginning in 1973 exposed Japan’s economic vulnerability, leading to an expansion of the nuclear programme

— Japan is involved in designing new reactors to be used domestically and exported overseas

— The Japan Atomic Energy Agency was established in 2005 from the merger of several other bodies. It employs 4,400 people and has an annual budget of 161 billion yen (£640 million)

— Japan’s 55 normally active reactors generate about one third of the country’s electricity. This is planned to increase to 41 per cent by 2014

Sources: JAEA; Uranium Information Centre

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